Much better and more stable handling of timezones for dates

The primary feature in this release is that Magic now (correctly) handles timezones, and also correctly associates the correct timezone with dates not having timezone information, if a "Default timezone" is specified. The only exception to this is the SQLite data adapter for everything except the log and tasks, since SQLite doesn't store date-time objects as such, but in fact stores these as strings in UTC format, without the trailing Z or other timezone specifiers.

However, all in all, date-time objects are now handled much better and more consistently as a general rule of thumb.